The present invention relates to an apparatus for lubricating the inside walls of moulds for blanks, for example moulds for compacting powdered materials into blanks for sintered parts.
The technique of compacting powdered materials generally provides for the use of suitable presses equipped with at least one plunger, one mould or die and a device for pouring the powdered material to be compacted into the mould and commonly called a filling shoe.
By compressing the powder poured into the mould by means of the filling shoe with the plunger, there is obtained a compacted part or blank, technically called a "green" moulding, which is thereafter subjected to the sintering process.
During the stage of compaction of the powder, frictional resistances are manifested which cause the dissipation of part of the load applied by means of the plunger.
These frictional resistances comprise:
1. friction between plunger and mould; PA1 2. friction between the grains of powder; PA1 3. friction between the mass of powder and the walls of the mould.
While the frictional resistance which is manifested between the grains of the powder produces cold microwelds and therefore confers greater strength upon the blank, the frictional resistances between the plunger and the inside walls of the mould and between the mass of powder and the walls of the mould contribute only to dissipating part of the load applied by the plunger and therefore reduce the useful load applied to the powder.